1. Field of the Invention
The present invention relates to a magnetoresistive transducer in general employed in a magnetic recording medium drive or storage device such as a magnetic disk drive and a magnetic tape drive. In particular, the invention relates to a magnetoresistive transducer including a magnetoresistive film extending over the surface of a fundamental layer such as a non-magnetic layer spreading over a lower shield layer, and a pair of domain control layers extending over the surface of the fundamental layer so as to interpose the magnetoresistive film along the fundamental layer.
2. Description of the Prior Art
A well-known magnetoresistive transducer is sometimes designed to include a spin valve magnetoresistive (MR) film, for example. The spin valve MR film allows the magnetization to rotate in a constitutive free ferromagnetic layer in response to the reversal of the magnetic polarity applied from the outside, as conventionally known. A relative angle defined between the rotating magnetization of the free ferromagnetic layer and the pinned magnetization established in a pinned ferromagnetic layer determines the electric resistance of the overall spin valve MR film. The variation in the resistance in response to the rotation of the magnetization in the free ferromagnetic layer can be utilized to detect the magnetic polarity of the applied magnetic field, for example, the magnetic bit data recorded on a magnetic recording medium. In this case, the single magnetic domain should be established in the free ferromagnetic layer of the spin valve MR film. This single magnetic domain of the free ferromagnetic layer is expected to greatly contribute to reduction in the Barkhausen noise.
A pair of hard magnetic layers magnetized in a so-called longitudinal direction are in general employed to establish the single magnetic domain in the free ferromagnetic layer. The hard magnetic layers interposing the spin valve MR film are supposed to establish the longitudinal bias field acting through the spin valve MR film. The longitudinal bias field is thus expected to greatly contribute to establishment of the single domain in the free ferromagnetic layer. However, the Barkhausen noise in fact cannot sufficiently be reduced in the magnetoresistive transducer irrespective of employment of the domain control hard magnetic layers.